OBD2 Fault Code Library

Free lookup for thousands of OBD2 trouble codes: filter by family, read short meanings, and open deeper articles. Desktop ELM327 scanner with live data and AI guidance.

OBD2 symptoms

Look up diagnostic trouble codes by what the car is doing: misfire, overheating, rough idle, a check engine light, and other common symptoms.

• Engine misfire
• Engine overheating
• Rough idle
• Check engine light
• Poor fuel economy
• Hard starting
• Engine stalling
• Catalytic converter efficiency
• Oxygen sensor fault
• EVAP leak
• Thermostat not reaching temperature
• Lean air-fuel mixture
• Rich air-fuel mixture
• EGR flow fault
• Engine knock
• Charging system
• Throttle position
• Mass airflow sensor
• Turbo underboost
• Coolant temperature sensor
• Transmission fault

• P250D — Engine Oil Level Sensor Circuit High (P250D): a powertrain (engine/transmission) fault affecting the sensor and actuator circuits. The car is usually drivable while you plan the repair. Most often caused by corroded, loose or damaged connector, blown fuse feeding the circuit, open or shorted wiring in the circuit.
• P250E — Engine Oil Level Sensor Circuit Intermittent/Erratic (P250E): a powertrain (engine/transmission) fault affecting the sensor and actuator circuits. The car is usually drivable while you plan the repair. Most often caused by control module driver fault, corroded, loose or damaged connector, poor ground connection.
• P250F — Engine Oil Level Too Low (P250F): a powertrain (engine/transmission) fault affecting the sensor and actuator circuits. The car is usually drivable while you plan the repair. Most often caused by poor ground connection, control module driver fault, faulty sensor or actuator of the affected circuit.
• P2510 — ECM/PCM Power Relay Sense Circuit Range/Performance (P2510): a powertrain (engine/transmission) fault affecting the sensor and actuator circuits. The car is usually drivable while you plan the repair. Most often caused by open or shorted wiring in the circuit, corroded, loose or damaged connector, blown fuse feeding the circuit.
• P2511 — P2511 — ECM/PCM Power Relay Sense Circuit Intermittent. A fault in the sensor and actuator circuits. The car is usually drivable while you plan the repair. Typical causes: open or shorted wiring in the circuit, poor ground connection, corroded, loose or damaged connector.
• P2513 — OBD2 code P2513 flags a problem with the sensor and actuator circuits (event data recorder request circuit low). The car is usually drivable while you plan the repair. Common culprits: poor ground connection, corroded, loose or damaged connector, open or shorted wiring in the circuit.
• P2514 — P2514 — Event Data Recorder Request Circuit High. A fault in the sensor and actuator circuits. The car is usually drivable while you plan the repair. Typical causes: poor ground connection, blown fuse feeding the circuit, corroded, loose or damaged connector.
• P2515 — A/C Refrigerant Pressure Sensor "B" Circuit (P2515): a powertrain (engine/transmission) fault affecting the sensor and actuator circuits. The car is usually drivable while you plan the repair. Most often caused by open or shorted wiring in the circuit, corroded, loose or damaged connector, poor ground connection.
• P2516 — A/C Refrigerant Pressure Sensor "B" Circuit Range/Performance (P2516): a powertrain (engine/transmission) fault affecting the sensor and actuator circuits. The car is usually drivable while you plan the repair. Most often caused by faulty sensor or actuator of the affected circuit, corroded, loose or damaged connector, blown fuse feeding the circuit.
• P2517 — OBD2 code P2517 flags a problem with the sensor and actuator circuits (A/C refrigerant pressure sensor "B" circuit low). The car is usually drivable while you plan the repair. Common culprits: poor ground connection, faulty sensor or actuator of the affected circuit, blown fuse feeding the circuit.
• P2518 — P2518 — A/C Refrigerant Pressure Sensor "B" Circuit High. A fault in the sensor and actuator circuits. The car is usually drivable while you plan the repair. Typical causes: open or shorted wiring in the circuit, corroded, loose or damaged connector, faulty sensor or actuator of the affected circuit.
• P251A — PTO Enable Switch Circuit/Open (P251A): a powertrain (engine/transmission) fault affecting the sensor and actuator circuits. The car is usually drivable while you plan the repair. Most often caused by corroded, loose or damaged connector, poor ground connection, blown fuse feeding the circuit.
• P251C — P251C — PTO Enable Switch Circuit High. A fault in the sensor and actuator circuits. The car is usually drivable while you plan the repair. Typical causes: control module driver fault, open or shorted wiring in the circuit, blown fuse feeding the circuit.
• P251D — P251D — PTO Engine Shutdown Circuit/Open. A fault in the sensor and actuator circuits. The car is usually drivable while you plan the repair. Typical causes: poor ground connection, blown fuse feeding the circuit, control module driver fault.
• P251E — OBD2 code P251E flags a problem with the sensor and actuator circuits (PTO engine shutdown circuit low). The car is usually drivable while you plan the repair. Common culprits: blown fuse feeding the circuit, faulty sensor or actuator of the affected circuit, open or shorted wiring in the circuit.
• P251F — P251F — PTO Engine Shutdown Circuit High. A fault in the sensor and actuator circuits. The car is usually drivable while you plan the repair. Typical causes: open or shorted wiring in the circuit, corroded, loose or damaged connector, control module driver fault.
• P2520 — P2520 — A/C Request "A" Circuit Low. A fault in the sensor and actuator circuits. The car is usually drivable while you plan the repair. Typical causes: control module driver fault, faulty sensor or actuator of the affected circuit, poor ground connection.
• P2521 — A/C Request "A" Circuit High (P2521): a powertrain (engine/transmission) fault affecting the sensor and actuator circuits. The car is usually drivable while you plan the repair. Most often caused by open or shorted wiring in the circuit, poor ground connection, corroded, loose or damaged connector.
• P2522 — OBD2 code P2522 flags a problem with the sensor and actuator circuits (A/C request "B" circuit). The car is usually drivable while you plan the repair. Common culprits: faulty sensor or actuator of the affected circuit, open or shorted wiring in the circuit, control module driver fault.
• P2523 — A/C Request "B" Circuit Low (P2523): a powertrain (engine/transmission) fault affecting the sensor and actuator circuits. The car is usually drivable while you plan the repair. Most often caused by faulty sensor or actuator of the affected circuit, control module driver fault, blown fuse feeding the circuit.
• P2524 — A/C Request "B" Circuit High (P2524): a powertrain (engine/transmission) fault affecting the sensor and actuator circuits. The car is usually drivable while you plan the repair. Most often caused by poor ground connection, open or shorted wiring in the circuit, corroded, loose or damaged connector.
• P2526 — OBD2 code P2526 flags a problem with the sensor and actuator circuits (vacuum reservoir pressure sensor circuit range/performance). The car is usually drivable while you plan the repair. Common culprits: control module driver fault, corroded, loose or damaged connector, open or shorted wiring in the circuit.
• P2528 — P2528 — Vacuum Reservoir Pressure Sensor Circuit High. A fault in the sensor and actuator circuits. The car is usually drivable while you plan the repair. Typical causes: blown fuse feeding the circuit, poor ground connection, control module driver fault.
• P2529 — Vacuum Reservoir Pressure Sensor Circuit Intermittent (P2529): a powertrain (engine/transmission) fault affecting the sensor and actuator circuits. The car is usually drivable while you plan the repair. Most often caused by control module driver fault, blown fuse feeding the circuit, corroded, loose or damaged connector.